Isolating switch systems for isolating an electric circuit of a motor vehicle from an electric power source are known and are specifically designed for a variety of uses. For example, there are known isolating switch systems in which a main line of the vehicle electric circuit is interrupted by pyrotechnic means in case of an accident. There are also known manually activated switches or isolating relays with a manually activated switch, with which a main line of a vehicle electric circuit can be interrupted.
EP 0 410 617 A2 shows an electronically controlled isolating switch system for controllably interrupting a main line between an electric power source and a consumer. This isolating switch system can be controlled as a function of the ignition switch of the vehicle.
However, for this the electric switching must be designed so that the electric circuit line is provided from the ignition switch of the vehicle to the isolating switch system, with which an appropriate control of the isolating switch system takes place. Subsequent integration of such an isolating ignition switch in accordance with EP 0 410 617 A2 into an existing electric circuit of a vehicle is therefore only possible when such a connecting line is incorporated between the ignition switch and the isolating switch system together with the isolating switch. However, this is complicated and cost-intensive.